The present invention relates to a method for optimization and control in the preparation of overlapping images used in reproduction processes and, more particularly, to such a method for optimization, control and standardization of multi-color reproduction processes such as, by way of example, those processes that are employed in the printing or reproduction of a number of copies or representations of an original image.
Presently known methods for producing reproductions in multi-color format generally have the following steps in common:
1. the production of images to correct, enhance or modify various values of subsequent image carriers, such as the production of masks, the use of which may be optional;
2. separation of the desired multi-colored image into its color components and recording each component on separate image carriers;
3. preparation, by any one of a variety of techniques, of subsequent image carriers which may be employed in any given reproduction process, such as plates or the like, for each separation; and
4. employing such plates or the like in any one of a number of well known printing processes, whereby reproductions are made through the use of different colorants, such as inks or dyes, placed in register to produce a multi-colored representation of the original image.
Other steps not mentioned above may include halftone conversions and the like. In any event, regardless of the particular process and the number of steps involved in the practice thereof, the results may be less than desirable when the final production is compared with the original image. Moreover, a lack of consistency may be apparent when the final products are compared to each other, much less to the original. This makes evaluation of the reproduction process all the more difficult due to the uncertainty as to which result is truly typical of the reproduction process.
The reasons for such inconsistencies and such undesired results are many; however, foremost among these are the inherent variabilities associated with the reproduction process, including those associated with the production of the original image or photograph itself and the pre-printing or pre-press areas as well as those associated with the printing of the reproductions. Turning to the area of printing the reproductions in general and to a newspaper press as a specific example, some of the variables involved are as follows:
1. skill of operators; PA0 2. variations in thickness of colorants; PA0 3. variations in colorant levels; PA0 4. variations in press speed; and PA0 5. variations in half-tone dot registration.
Thus, even assuming the pre-printing or pre-press operations and procedures can be held relatively constant, the pressures of time, economy and the like dictate against precise control over all the variables associated with a particular machine or press employed to print the reproductions in large quantities. More importantly, even attempts to control one or more of the variables involved may not lead to a satisfactory reproduction when compared to the original on a routine, periodic basis in as much as presently employed measuring techniques are inadequate to accurately represent the desired results. There is, thus, lacking a method of measurement that optimally correlates the original with the intended or desired final reproduction on a consistent and regular basis, much less permitting an objective statement of the desired results should the original be less than satisfactory.
However, in practice, problems in variability are associated with present techniques employed in the pre-printing or pre-press operations. These areas as taken here, involve all the steps from the picture-taking through separation to plate making.
In present practice, the original photo or image submitted for reproduction may consist of a negative, an internegative, a positive transparency, a print or even an electronically reproduced image. In any case, a decision is made that this original is what is desired to be reproduced. However, since such decision is usually subjective, based on experience, and since the human eye is capable of resolving errors or correcting for incorrect color balance or for different light sources, it is not surprising that the final reproductions often do not compare favorably to an accurate representation of what was really desired. In an attempt to overcome this problem a number of measuring techniques are available and utilized. One technique measures neutrals in the image and is based on the assumption that there are neutrals to measure and that the operator will be able to identify what should be neutral so that he can make the measure. Another technique measures flesh tones (or some similarly identifiable color); however, since flesh tones vary considerably in color, this technique is dependent on chance, operator skill or both. A third technique assumes that integration of all the colors within the original will balance out to neutral and an attempt is made to measure the mix of colors in the original. As above, this technique is also a matter of chance and/or operator skill. A further technique employs the use of a separate gray scale which is measured to determine separation values; however, this technique is based on the unlikely assumption that the original is perfect. It should be apparent, accordingly, in the pre-printing or pre-press stage of the entire reproduction process there is similarly lacking a method of measurement that optimally correlates a original with a desired final result on a consistent and objective basis.